The reference J. Latimer, Automatic Welding, deals with the control of the arc length during submerged arc welding. A constant-current power source with usually larger wire diameters is used here, and slight changes in the amount of arc and thus in the arc voltage cause only a slight change in the current intensity. The arc length, which may change because of different effects, can be controlled by changing the electrode feed speed. The voltage is tapped for this purpose from the terminals of the current source or from the contact tube. The electrode feed speed is reduced when the arc length decreases and a corresponding voltage drop occurs, and, conversely, it is increased as the arc length increases. The welding current source is designed as a constant-current power source and is not controlled. U.S. Pat. No. 3,054,885 shows a system for monitoring a plurality of welding units by one operator. In the case of disturbance in one unit, this unit switches itself off and signals the failure to the monitoring operator, who is then to eliminate the disturbance. The monitoring is performed via various relays.